Turntable drives for record players



Dec. 30', 1958 e. o. GABRIEL TURNTABLE DRIVES FOR RECORD PLAYERS 5 Sheets-Sheet 1 Filed May 2, 1967 Dec. 30, 1958 G. Q. GABRIEL 6 TURNTABLE mamas FOR RECORD PLAYERS Filed May 2, 1957 5 Sheets-Sheet 2 Dec. 30, 1958 G. Of GABRlEL TURNTABLE: DRIVES FOR RECORD PLAYERS INVENTOR. V fiW ,2 W'

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TURNTABLE DRIVES FOR RECORD PLAYERS Filed May 2. 1957 r 5 Sheets-Sheet 4 INVENTOR Dec. 30, 1958 s. o. GABRIEL TURNTABLE DRIVES FOR RECORD PLAYERS Filed May 2, 1957 5 Sheets-Sheet 5 United States Patent "ice TURNTABLE DRIVES FOR RECORD PLAYERS Gustave 0. Gabriel, Washington Court House, Ohio Application May 2, 1957, Serial No. 656,712

Claims. (Cl. 74-745 This invention relates to turntables for 1 sound reproducing devices, such as hi-fidelity record players.

Turntables for record players. are deficient in many respects and experts in the art recognize that a real need exists for a turntable that will cure these deficiencies.

In the book The High-Fidelity Reader edited by Roy H. Hoops, Ir., Hanover House, Garden City, New York, 1955, there is an article Servicing a home music system by Irving M. Fried, pp. 158185 in which turntables and drives therefor are discussed. On pages 173- 174, the article particularly points out serious deficiencies in turntables and the drives therefor as follows: The above examples are not intended to damn the brand names mentioned, but to show that cartridges and turntables of all kinds are subject to troubles from neglect and lack of maintainance. The writer offers the following summary of his experience in making various kinds of turntables and pickups perform at their optimum.

Turntables should be easy to set up and maintainall they have to do is to turn around. And yet, one of the great development laboratories in this field states categorically that there is no completely satisfactory turntable available today, at any price. to the following:

(1) Flutter: a rapid change (acceleration and deceleration) in groove-speed which imparts, for example, a heavy vibrato to a soprano and makes a flute sound like a quivering reed.

, (2) Wow: a once around or slow-speed variation in groove-speed. Sustained notes will go off pitch and on pitch, to the exasperation of the music lover.

(3) Rumble: mechanical noise transmitted into the pickup and out of the loudspeaker, of low-frequency nature. At best, an irritation; at worst, of such amplitude that many amplifiers and speakers will be overloaded at the critical low-frequencies, with resultant severe distortion.

(4) Speed: many turntables are consistently oii speed. As a result music is played back in new key relationships.

On pages 175' and 176 of the article by Fried in the book The High-Fidelity Reader supra, it is pointed out that rim-driven turntables are subjected to the following difficulties time and again:

(1) Motor vibration.

(2) Out-of-round pulleys.

(3) Other irregularities, such as burrs, flats, cuts in the pulleys, etc.

(4) Old pulleys.

(5) Tightbearings.

Motor vibration and electrical noises show up in the quality of the music reproduced by the record. Motors that do not operate at constant speed, such as the shade pole or induction motors produce variations in tonal pitch and speed adjustments are difficult to make. All these difiiculties are thoroughly discussed in the book.

There is also an article in the magazine Consumer Reports by Consumers Union of U. S., Inc. September 1956, volume 21, No. 9, pp. 429-434 on Hi-fi turntables.

Turntables are prey 2,866,362 Patented Dec. 30, 1958 That article discusses the virtues and faults of turntables on the market and classifies them according to overall value based on quality, performance and price. The article defines a turntable as follows:

A turntable consists of a fiat disc, a motor, and a drive mechanism which transmits the motors rotation to the disc. Although this is essentially a simple system, a high degree of perfection is demanded. The turntable should rotate at exactly the right speed at all the speed settings provided. It should maintain a constant speed through every moment of play. It should not introduce noise into the system. And it should be convenient to operate.

Continuing at pp. 429' and 430 of the Consumers article supra, it is stated:

A prime requisite for a high-fidelity turntable is relatively exact speed; if the turntable runs too slowly the record music will be played at a lower pitch and slower tempo than was intended; if the table is too fast, the pitch will be too high and the tempo too fast. Turntable troubles which affect speed accuracy may stem from the motor or from the drive mechanism. For instance, in addition to the errors in precision of manufacture which will aifect speed, the drag of the pickup stylus in the record grooves can cause the drive to slip; variations in line voltage can change the speed of an induction motor. Following the abovequotation, the article comments on the types of motors, synchronous and induction. It then goes on to say:

Regardless of the type of motor used, speed inaccuracies may enter from still another source, the drive mechanism which steps down the fast-turning motor (about 1800 R. P. M.) to the slow turntable speeds. Speed reduction could be accomplished, as it is in an electric clock, by a direct gear drive which could not slip, but

noise from the rigidly coupled gears and speed uneveness resulting from imperfect gears could then become problems. Most turntables utilize a friction drive-a gearless system which generally employs smooth rubber idler wheels to transmit power from the motor shaft to the turntable rim. Some friction drives utilize a belt between motor shaft and rim. But a friction drive is almost certain to be subject to some drift in speed over a period of time; wear, changes in temperature, changes in the pressure of the idler against motor shaft and turntable rim and in the drag of the stylus as it traverses the record, all cause variations in speed. All friction drives have some amount of slip in the transfer of motor rotation to the table. With good design it is possible to minimize these effects.

On page 431, the article discusses flutter and wow and its causes. It also discusses Rumble and Hum as follows at page 431:

Turntables generate various kinds of noise which are picked up and amplified, and emerge from the loudspeaker to mar enjoyment of the music. Motor vibrations, bearing noise, idler noise-all may be transmitted to the pickup and heard through the loudspeaker as lowpitched, rumbling sounds. This noise, known as rumble, is most commonly heard during relatively quiet passages of music.

Another kind of noise can be traced to the magnetic field of the motor, which causes an induced hum in a magnetic pickup used with the turntable. On some turn-j tables this hum was quite audible during quiet passages record player turntables which has no direct mechanical connection with the turntable and which is quiet and overcomes the objections above stated.

Another object of the invention is to provide a turntable drive and motor combination that will provide exact and constant speed of rotation of the turntable and be free of rumble, wow,.flutter and other objections.

A still further object of the invention is to provide a drive whereby turntables may be driven at constant but easily adjusted different speeds, that shall be simple in construction, economical to manufacture and efiicient and long-lasting in operation.

Another object of the invention is to provide a multispeed turntable drive provided with means for changing the speed of the turntable to one of a number of possible speeds by the simple expedient of turning a single knob or indexing member.

The above and other objects of the invention will be apparent to those of ordinary skill in the art to which the invention pertains from the following description taken in conjunction with the accompanying drawings.

In the drawings:

Figure 1 is a top plan view of a turntable for a record player and the drive assembly therefor, including the motor, the drive being arranged and constructed in accordance with an embodiment of the invention;

Fig. 2 is a view in side elevation of the assembly shown in Fig. 1, parts thereof being in section, and parts being broken away;

Fig. 3 is an enlarged view in section partly fragmentary of the turntable drive assembly embodied in the illustration of Figs. 1 and 2;

Fig. 4 is a top plan view of the turntable frame or platform and the turntable, parts being in section, showing the element that drives the turntable without contact therewith;

Fig. 5 is an enlarged partial view of the turntable rim and the driving element showing the momentary contact between the driving element and the table at the instant of starting;

Fig. 6 is a fragmentary view in section taken on line 66 of Fig. 4;

Fig. 7 is a view in section taken on line 77 of Fig. 3 showing a driving pulley on the input shaft and a driven pulley on the output shaft of the turntable drive;

Fig. 8 is a plan view of a pulley on the output shaft of the turntable drive;

Fig. 9 is a view in section taken on line 9-9 of Fig. 3 showing a clutch shifter fork mechanism and a cam operator for operating the shifter fork associated with one of the pulleys on the output shafts of the turntable drive;

Fig. 10 is a view in section taken on line 1010 of Fig. 3; and

Fig. 11 is a view in section taken on line 1111 of Fig. 2.

The adjustable speed drive mechanism of the invention is so designed that the output shaft thereof may be driven at a selected one of a plurality of speeds. To simplify illustration and description, the drive mechanism is illustrated as provided with three different speed adjustments of the output shaft. A different number of speed adjustments may be incorporated in the drive if'desired as will be apparent from a detailed description of the illustrated embodiment. While the drive is suitable for various purposes, it is shown and described as a drive for turntables .for sound recording and reproducing equipment.

shown) carried by the frame, the shaft also serving to center a record disc.

The turntable frame 2 may be of standard construction and provided with a depressed or sunken bottom 5 surrounded by a mounting lip or border 6. The motor and drive assembly 3 are carried by the bottom 5 as shown in Fig. 2.

Assembly 3 comprises a main support plate 7 and a support plate 8 which is secured in spaced relation to the plate 7. The plates 7 and 8 are separated by rubber or elastomeric shock absorbers 9. Similar shock absorbers 10 and 11 are placed on the bottom of plate 8 and the top of plate 7. .The plates 7 and 8 and their shock absorbers are secured firmly together with screws 12 by means of which the motor and drive assembly may be attached to the bottom 5 of the frame 2.

The assembly also includes a motor 13, an input shaft 14 driven by the motor through a worm 15 on the motor shaft 16 and a wormwheel 17 on the input shaft 14. The assembly further includes an output shaft 18 that is parallel to shaft 14 and driven by the same at selected speeds as will be described infra.

The output shaft 18 has at its upper end a multipole magnetic driver 19 that cooperates with a ring 20 mounted on the inside face of the turntable rim flange 21, to drive the table. The ring has a predetermined number of salient magnetizable pole tips 22 and the driver 19 has a predetermined number of magnets 23 of permanent magnetic material so arranged that the north and south poles thereof alternate as shown in Fig. 4. The outer ends of the magnets may be spaced from the pole tips 22 a distance of 0.001" to 0;003". Experimentation may show that a different spacing is more suitable in a given case.

The driver 19 is provided with a non-magnetic plate 24 having fingers 25 disposed between the magnets 23 and arranged to project radially into the space between the poles on the ring 24) as the driver rotates. The fingers are employed for the purpose of providing quick starts of the turntable overcoming the inertia thereof without slippage. After the table is up to speed, it runs in synchronism with the driver 19, at which time the fingers do not engage the poles of the table pole ring 29 as they operate between and in spaced relation to them as shown in Fig. 4. At the instant of. starting, a finger 25 engages a pole 22 as shown in Fig. 5. Since the motor reaches synchronous speed in one or two cycles of the supply voltage, only one or two of the fingers would engage the turntable ring poles from standstill to full speed of the table. After that, the table is driven magnetically without any physical contact between the table and the driver 19.

At this point the motor speed and the reduction from the motor shaft to the turntable should be considered on the assumption that the table is to have three speeds to meet the particular requirements of records to be played, or cut. For purposes of this case, it may be assumed that the table speeds will be 16 /3, 33 /3 and -45 R. P. M., respectively, and that the shaft 16 of the motor runs at 1800 R. P. M. at synchronous speed. The first reduction is between the motor shaft 16 and the input shaft 14. That reduction can conveniently be a ratio of 10 to 1 so that the input shaft 14 runs at R. P. M. at a motor speed of 1800. To obtain the three table speeds mentioned, a fixed reduction is provided between the driver 19 and the table 1 and adjustable reductions between the input and output shafts 1 and 18.

The fixed reduction between the driver 19 and the table may be in the ratio of 72 to 18 or 4 to 1. Thus, if the driver 19 has 18 bar magnets 23 and the ring 20 has 72 salient poles, a ratio of 4 turns of the driver to one turn of the table is obtained, or a reduction ratio of 4 to 1. To obtain a rotational table speed of 16% R. P. M., the output shaft 13 must be driven at 66 /3 R. P. M. which means that the reduction between the input and the output shafts will be in the ratio of 180 to 66 2s or approximately 2.7 to 1.. At 33% R. P. M., the reduction between the input and output shafts is in the ratio of approximately 1.35 to 1 and at 45 R. P. M. the ratio is 1 to 1.

The above stated reductions are obtained by means of pulleys on the input shaft having equal pitch diameters and three separate pulleys of different pitch diameters on the output shaft and a belt for each pair of table speed pulleys on the output shaft 18. Each of the output shaft pulleys is provided with a clutch and all clutches are actuated lay a single selector so arranged that only one pulley can be engaged with the output shaft at one and the same time.

The input shaft 14 is supported at its lower end in a bearing bracket 27 of L-shape having a horizontal leg 28 and a vertical member 29 that is secured to the motor with screws 36. The bracket 27 may be a die casting and provided with a bearing socket 31having at the bottom thereof a palate 32 of material such as nylon or Teflon and a sleeve bearing 33 of a material such as nylon. the palate 32. The upper end of the shaft is supported in a bearing 35 having a housing 36 and a flange 37 that is secured to the plate 8. The bearing 35 is similar to the bearing at the upper end of the output shaft 18 which is shown in section.

The motor 13 is secured to the plate 8 by means of an inverted U-shaped bracket 40 having depending arcuate members 41 disposed on each side of the stator 42 and secured thereto by means of bolts 4-3. The bracket 40 may be welded or otherwise secured to the member 8. As shown in Fig. l, the plate 8 is secured to plate 7 at three points by screws 12. The plate 8 is provided with elongated slots 8' through which the screws pass which providesa means of adjusting the tension in the drive belts. v When that adjustment is made, the motor and the input shaft with its pulleys are moved as a unit.

The wormwheel 17 as shown is secured by a pin 45 to the shaft 1 The wormwheel may be of Teflon and the worm 15 may be of steel and provided with double pitch threads so that the reduction between the motor shaft 16 and the shaft 14 may be in the ratio of 10 to 1 for the particular case under consideration.

On the shaft 14 are three pulleys 46, 47, and 48. These pulleys are identical in construction and have equal pitch diameters. Each pulley includes a body 49 having a flange 50 on its upper face and a removable metallic disc 51 which forms the lower flange of the pulley. The body of the pulley has a hub 52 that extends through an aperture in the disc 51. The pulley hub 52 is secured to the shaft 14 by means of a pin 73 that extends through the hub 52 at such a location below the disc 51 that it retains the disc flange 51 in place. The pulley 46 drives an endless belt 54 of a suitable plastic. To prevent slippage between the belt and the pulley, the pulley is provided with uniformly spaced concavities 55 that receive similarly shaped projections 56 on the driving face of the belt. The pitch diameter of the pulley is indicated by the dimension D. -That diameter is fixed by the ratio of reduction between the pulley 46 and the output shaft 18 which is required for a particular table speed. The pulleys 47 and 48 are similarly constructed and have the same pitch diameter D. The pulleys 47 and 48 drive belts 57 and 58 of the same construction and composition as the belt 54.

The output shaft' 18 is supported at its lower end in a bearing assembly 59 securedto a plate 60. The plate 60 is supported from the plate 7 by struts 61 and 62, see Figs. 2 and 3.

The shaft 18 has mounted thereon pulleys 64, 65 and 66 having pitch diameters D D and D Any pulley on shaft 14 and its driven pulley on shaft 13 constitute a pulley pair. These pulleys are provided with ball bearings 67, 68 and 69 so as to be free-wheeling on the shaft 18 except when coupled thereto by a clutch. As shown, the pulley 64 is larger in diameter than the pulley 65 The shaft is supported on a ball 34 that engages and it in turn is larger than the pulley 66. The ratio of the pulley diameters D:D DzD and D:D are such that when the pulley 64 is engaged, the shaft 16 provides the 16% R. P. M. rotation of the turntable, the pulley 65 when engaged with the shaft provides the 33% R. P. M. and the pulley 66 provides the 45 R. P. M. rotation of the table.

To facilitate assembly of the various pulleys on the shaft it will be seen in Fig. 3 that the shaft is stepped so that the larger pulley and its bearing 67 may he slipped on the shaft first to its intended position. The stepping of the shaft also provides shoulders for retaining the ball bearings in place on the shaft.

The pulley 64 comprises a member 70 having a flange 71 on its upper face. The pulley 7G and the flange 71 may be made of a material such as Bakelite. The bottom face of the pulley is provided with a metaillic disc 72 that is secured to the pulley body 70 by means of pins 73. The disc 72 is provided with a plurality of uniformly spaced downwardly extending projections 74 that serve as clutch teeth.

The pulley 64 is provided with a clutch 75 having a hub 76 and upper and lower flanges 77 and 78. The hub is coupled with a crescent key 86 to the shaft 18 and is slidable vertically thereon. The upper flange 77 is provided with recesses 81 for receiving the projections 75 on the disc 72.

The clutch may be actuated to or from engagement with the pulley 64 by means of a shifter fork 82.

The pulley body 70 is provided with spaced recesses 83 for accommodating the projections 55 on the belt 53. The pitch diameter D of the pulley body 76 is turned to precise size so that the reduction from the input shaft 14 to the output shaft 18 will correspond to the exact reduction required, the 16 /3 R. P. M. speed of the table.

The pulleys 65 and 66 are identical in construction except for size and are provided with ball bearings as shown so that the pulleys are free-wheeling on the shaft 18 except when in driving engagement with the shaft through its clutch. The clutch for the pulley 65 is indicated at 76a and the clutch for the pulley 66 at 76b.

The shaft 18 as shown is supported at its lower end in the bearing assembly 59. That assembly comprises a housing or retainer 85 having a flange 86 secured as with rivets to the plate 60. In the bottom of the housing 55 is a palate 87 of a material such as nylon and having at its center a ball 88 on which the end of the shaft rests. The shaft is guided in a sleeve 59 of a material such as nylon.

The pulley bodies of pulleys 64, 65 and 66 may be formed of molded Bakelite and the plates '72, 72a and 72b may be made of metal. The clutches 76, 76a and 76b may be made of metal.

The upper end of the shaft 18 is supported in a hearing assembly 91 that comprises a housing 92 having a flange 93 secured as with rivets 94 to the plate 7. Within the housing 92 is a sleeve bearing 95 of a material such as nylon.

The clutches 76a and 7612 are actuated to or from engaged position by means of shifter forks 96 and 97.

The construction of the shifter forks 82, 96 and 97 are identical. As shown in Fig. 9 fork 82 comprises a bifurcated portion 98 having an arm 99 that is mounted on a pivot 1% supported by a post 161. The inner ends of the portion 98 are provided with wheels 1592 that ride between the flanges 77 and 78. The wheels 102 may be of nylon or Teflon and mounted on trunnions 103 carried by the ends of the portion 98. At the opposite end of the arm 99 is a roller 104 secured to the arm 99 by means of a screw 105. Similar and corresponding parts of the shifter fork 96 and 97 are designated by the same reference characters with appropriate subscripts affixed.

The post 101 as shown rests on the plate 66' and is retained by means of a cap screw 1% threaded into the lower end thereof. The upper end of the post is stayed 7 by means of a bracket 106 the lower end of which is 'secured to the plate 60 by means of a bolt 107. The upper end of the bracket is apertured to receive a reduced end portion of the post 101, which is peened onto the bracket to securely fix it in position.

The clutches are actuated by a single control means that comprises a shaft 108 having thereon shifter fork actuators 109, 110 and 111 for shifting the clutches 76, 76a and 76b, respectively. The actuators being similar in construction, the parts thereof may be identified by the same reference characters with appropriate differentiating subscripts.

The actuator 109 comprises a hub 112 having spaced cam plates 113 and 114 thereon. The plates 113 and 114 are provided with depressions 115 and 116 located directly above one another. Thus when the shaft 108 is turned so that the depression 115 is on top of the roller 104, the shifter fork is rotated clockwise on its support pin thereby shifting the clutch into engaged position with its pulley 64. When the roller 104 rides on the fiat surfaces of the plates 113 and 114 the clutch is in disengaged position.

The shifters 110 and 111 are identical to the shifter 109 except that the depressions 115a-116a and 115b 1161; are located in different angular positions.

In order to retain the shaft 108 in a selected speed position or in an off position, it is provided with an index plate 117. The edge of that plate is provided with spaced recesses 118 to 122, respectively, that receive a roller 123 mounted at one end of a cam lock lever 124. The lever 124 is pivoted on a pin 125 and is biased in a direction to cause the roller 123 to follow the cam surface of the plate 117 by means of a tension spring 126. The shaft 108 is provided with an indexing knob 127 (see Fig. 1). That knob can be turned clockwise or counterclockwise from the 16% R. P. M. to the 45 R. P. M. position or vice versa. Between each speed position is an off position. Therefore, as shown, the recess 118 on the index plate 117 corresponds to the 45 R. P. M. position, the recess 119 to an off position, the recess 120 to the 33 /3 R. P. M. position, the recess 121 to an off position and the recess 122 to the 16 /3 R. P. M. position.

The assembly as shown in Fig. 3 is a complete unit "or assembly. It could include the motor and be made and sold separately from the table frame 2.

The driver 19 comprises a hub or disc 128 keyed to the upper end of the shaft 18 which is reduced in diameter at the point where it passes through the hub. The periphery of the hub 128 is provided with sockets 129 to accommodate the bar magnets 23. These magnets have a press fit with the sockets so that they are firmly retained therein. The plate 24 as shown is mounted on top of the hub 12%) and may be retained in place with a key or snap ring. The rim of the plate 24 is radially slotted to provide the fingers 25 which as shown are turned downwardly and project outwardly of the ends of the bar. magnet so that they will extend into the spaces between the pole 22 on the ring 20.

The ring 20 may consist of a pair of cold rolled steel plates appropriately punched to provide the teeth or poles as shown. These plates are riveted together. The outside diameter of these rings is such that they can be press fitted into a recess 129 in the table flange 21.

With the construction shown in Fig. 6, the table 1 may be made of aluminum. If the table is of cast iron, the poles 22'.- may be formed integrally with the flange thereof. If an aluminum table is employed the tone or pick up arm of the machine may be shielded by adhering steel wool to the frame bottom at a location above the driver 1). Cast iron tables are sutficiently self-shielding and do not require the steel wool.

In the adjustable speed drive assembly above described it will be apparent that there is no slippage between the input shaft 14 and the output shaft 18 because the pulleys on the input .and output shafts are provided with the arcuate recesses that receive the depressions 55 on the belts. The belt projections 55 do not serve as gear teeth, they merely act as stops between the belt and the pulleys. In other words, assuming the pulley of Fig. 7 to be rotating in the direction of the arrow, it will be apparent that the initial slippage, if any, will only be that amount of travel which will cause the trailing edge of the projection 55 to engage the leading edge of a tooth or recess 54. As soon as the tooth engages the trailing edge of the projection, there is no further slippage. Similarly, the same action takes place between the belt and the driven pulleys on the output shaft.

Since the speed relationship between the input and the output shafts is fixed, it follows that the output shaft 18 will have a fixed speed with reference to the motor shaft.

There is no slippage between the driver 19 and the turntable rim because the induced poles in the ring 20 will take a locked position with respect to the poles of the magnets of the driver 19, just as the poles of rotor of a synchronous motor lock in step with the rotating field thereof. Therefore, as there is no slippage between the driver 19 and the turntable and no slippage between the input shaft 14 and the output shaft 18, it follows that the turntable speed will have a fixed relationship to the speed of the motor, and if the motor is a synchronous motor the turntable will run at a fixed, constant speed for each speed setting.

Furthermore, the mechanism for changing the speed of the turntable is simple and direct, the change from one speed setting to another being accomplished by the simple expedient of turning the indexing knob.

While the invention has been illustrated in connection with a turntable of a record player or record recorder, it will be apparent to those of ordinary skill in the art that the drive has other applications where fixed relationships are required between the input shaft of the mechanism to the output shaft.

Having thus described the invention, it will be apparent to those of ordinary skill in the art to which the invention pertains, that various modifications and changes may be made without departing from either the spirit or the scope of the invention.

Therefore, what is claimed as new and desired to be secured by Letters Patent is:

1. A no-slip adjustable speed drive for turntables of record players and recorders comprising in combination a motor, an input shaft driven by the motor and having a plurality of transmission pulleys secured thereto, an output shaft having a plurality of pulleys thereon one for each input shaft pulley, said pulleys being freely r0- t'ttable on the shaft and being of different diameters relative to the corresponding pulleys on the input shaft, each pulley on the input shaft forming with a corresponding pulley on the output shaft a pulley pair, a belt running over each pulley pair, each belt and the pulleys of a pulley pair having intermeshing means for preventing relative slippage between them, clutch means for each output shaft pulley for engaging the same with the output shaft, a cam assembly for controlling said clutches and selectively engaging one of said clutches while disengaging the others from said output shaft, a magnetic driving member secured to the output shaft and having a plurality of radially extending circumferentially spaced permanent magnets, the outermost ends of said magnets being at the same distance from the center of the output shaft, a magnetizable ring on the turntable having integral inwardly extending pole pieces arranged to be attracted by the magnets on said drive member, and means on said magnetic drive member for engaging said pole pieces only during the commencement of rotation of the magnet driving member, the ratio of the number of permanent magnets to the ratio of pole pieces on said ring corresponding to the relative rotational speed desired between said output shaft and said turntable.

aseesea 2. A multispeed drive for sound recording and reproduction turntables including a vertically positioned output shaft below the turntable, a power input motor operable shaft parallel thereto, a multispeed belt drive connecting said shafts for operating the output shaft at the selected speeds, the pulleys being provided with uniformly spaced recesses on the peripheries thereof and the belts with uniformly spaced projections adapted to be received in said recesses, a manually operable cam shaft arranged to control the speed ratio, magnetic driver fixed on the upper end of output shaft, including a circular series of permanent magnets projecting radially and of alternately Opposite polarities at their outer ends, the turntable having a depending flange ring provided with inwardly projecting magneti; ole teeth ar ranged in circular series, the driver being in the plane of the toothed ring and having the extremities of its magnets operating in close proximity to thetecth the ring without physical contact, whereby the turntable may be driven at a selected speed without mechanical contact of the driver.

3. A magnetic drive for a record turntable comprising a ring attached to the turntable and having a circular series of inwardly directed magnetizable teeth, a rotary driver having a smaller circular series of outwardly projecting permanent magnets of alternately opposite polarity for operation in the plane of the ring and having a pitch spacing corresponding to the pitch of the ring teeth, the

driver being so positioned that the extremities of its magnets move into close proximity to the extremities of the ring teeth without physical contact, and so transmit driving force without friction or vibration, said driver having thereon radially spaced non-magnetic teeth adapted to be received between the teeth of the turntable ring for the purpose of overcoming inertia of the turntable at the instant of starting.

4. A magnetic drive as in claim 2 in which a starter plate is connected to the driver and provided with proiecting fingers entering the spaces between the teeth of the ring to transmit mechanical force by contact with the teeth during changes of relative speed but remaining out of contact during normal operation at constant speed ratio.

5. An adjustable speed transmission for record player turntables, said transmission having an input shaft adapted to be driven by a motor, an output shaft and a no-slip adjustable speed belt drive connecting said shafts, said drive comprising a plurality of pulleys fixed on the input shaft, a plurality of pulleys rotatably mounted on the output shaft, one for each pulley on the input shaft, each pulley on the input shaft forming with a corresponding pulley on the output shaft a pulley pair, the diameters of the pulleys on the output shaft being different from the diameters of the pulleys on the input shaft to provide a plurality of ratios of the R. P. M.s of the input to the output shaft, a belt for each pulley pair, each of said belts and the pulleys of each pulley pair being provided with means for preventing relative slippage between them, clutch means for each output shaft pulley for engaging the same with the shaft, and cam controlled means for selectively engaging only one of said clutches at a time, said cam controlled means comprising a pivotally supported shifter for each clutch, each shifter having a bifurcated end having relative rotational engagement with its clutch, a cam shaft having thereon cam members each provided with an annular groove for receiving the end of the shifter opposite the bifurcated end, the grooves of the respective cams having cam lobes for rocking the respective shifters to or from clutch engaging position, the lobes being so angularly spaced with reference to each other that only one clutch can be engaged at a time.

References Cited in the file of this patent UNITED STATES PATENTS 1,819,889 Getz Aug. 18, 1931 2,044,599 Weinreich et al June 16, 1936 2,308,090 Macfarren Ian. 12, 1943 2,445,310 Chilowsky July 20, 1948 2,674,896 Arones Apr. 13, 1954 

